This invention relates to a remote control system and, more particularly, to such a system wherein any desired one of plural devices may be controlled by the transmission of a remote control signal to any one of plural, spatially separated receiving elements. The present invention is particularly advantageous for use in a remote control system wherein the remote control signal is transmitted with relatively high directivity.
It now is common in so-called home entertainment systems to provide control circuitry by which a user of that system may control particular home entertainment devices included therein. For example, a typical home entertainment system may include a television receiver, a video tape recorder (VTR), a cassette recorder, a radio tuner, an audio amplifier, a phonograph turntable, and the like. Selective ones, or all of these devices preferably are controlled by the user from a remote location. For example, such devices may be turned ON or OFF, volume may be adjusted, channel or broadcast station may be selected, particular portions of a pre-recorded tape or a phonograph record may be reproduced, and the like. Such functions are achieved by transmitting a command signal from a transmitter unit to a central control for the devices. The command signal may be a coded signal and may modulate an ultrasonic carrier, a radio wave carrier, or the like, for transmission from the transmitter unit to the central control. At the central control, the modulated signal is received and decoded to produce a corresponding control signal. Hence, depending upon the particular control signal which had been encoded, a desired one of the controllable devices may be turned ON or OFF, and a particular function thereof may be selectively controlled, as mentioned above.
Desirably, the remotely transmitted control signal exhibits relatively high directivity. This is advantageous in order to avoid false triggering or actuation of the central control by spurious signals. One type of carrier which exhibits desirably high directivity is an infrared carrier. In one remote control system of the aforementioned type, although plural devices may be controlled, the central control generally is provided with only a single receiving element. While the desired device may be suitably controlled when the encoded, infrared remote control signal is transmitted to the receiving element, the user often directs his transmitter toward the particular device which he wishes to control. Hence, because of the desirably high directivity of the remote control signal, this signal is not received at the receiving element. Consequently, the device which the user wishes to control is not controlled. Because of this, the user often is of the mistaken belief that either his command transmitter, or the central control, or the particular device which he wishes to control is in disrepair.
This mis-direction of the transmitted remote control signal occurs frequently in a system having master and remote television receivers, both of which are controlled by a common television tuner. In this arrangement, the receiving element usually is provided directly at the common television tuner. Hence, when this master/remote television receiver system is desired to be operated by the user, the remote control signal must be transmitted to the receiving element at the common television tuner. It is not unusual, however, for the user to direct the transmitted remote control signal to the master or to the remote television receiver which, of course, fails to operate in the manner which he desires.